Table of Contents
TopicsYou've made your 3D model, but how do you get your tooling?
Creating a well-designed part for injection molding is half the battle - making the tooling is another animal entirely.
Note: If using a supplier to produce your parts, you need only submit your part to the supplier, and they will usually take care of injection mold tooling. If you’re in a situation where you need to design your own tooling, this post is for you.
The instructions in this post are intended for molds that use core and cavity tooling, comprising of an estimated 70-80% of all injection molds. Specialized tooling, such as using slides, are not covered in this post, though the method in this post may be a good first step in getting slides for your tooling.
Note: If using a supplier to produce your parts, you need only submit your part to the supplier, and they will usually take care of injection mold tooling. If you’re in a situation where you need to design your own tooling, this post is for you.
The instructions in this post are intended for molds that use core and cavity tooling, comprising of an estimated 70-80% of all injection molds. Specialized tooling, such as using slides, are not covered in this post, though the method in this post may be a good first step in getting slides for your tooling.
With every meeting, there is a parting (line)
Injection mold tooling primarily consists of a cavity and core. Once they are placed together, the negative space between the two tools is filled with heated plastic to form into the shape the designer desires. The line where the two tools meet is known as the parting line. A well-designed injection molded part will have been created with this parting line in mind. This will be a driver for how the tooling is designed.
Injection mold tooling design for simple parts - keeping your designs watertight
In the simplest of cases, the tooling can be generated by creating a block in CAD, then importing the part to be molded and aligning the parting line on the edge of the block. The core and cavity can be generated by performing a simple subtractive Boolean operation.
There is one important characteristic that makes this method work:
The part has been designed such that there is no contact between tools or features crossing over the parting line.
Being watertight allows the two unique bodies of the cavity and core to be generated with one Boolean operation. But if the part had a hole, pass-through shutoff or other features that would not be watertight to the parting line, the Boolean would not produce a separate core and cavity, but one single part that has a negative cut in it- not what we want. The stool in this example was unable to generate a distinctive core and cavity.
What are we to do if such a situation arises?
The Boolean Method
Just as there are many ways to do something in parametric CAD to arrive at the same result, there are numerous ways to deal with generating injection molded parts. The following procedure is just one way that tooling for injection molded parts may be generated.
1. Make sure your part has good integrity, perform a save-as and create a new version of your part. Make this version with added and removed features to create a watertight part. Do not remove any features that are not necessary to remove.
2. Use the new watertight version of the part to Boolean to create a watertight core and cavity. It is recommended to save the core and cavity as separate files.
3. Save the watertight Boolean version of the file as a new file and subtract out the original part. What remains are all the changes you made to your watertight version of the file and nothing else. These will exist as individual bodies floating in space.
4. Of the bodies floating in space, identify which belong on the core tooling, and if any, which belong on the cavity tooling. Boolean unite each of these bodies to the appropriate tool
5. Create an assembly of the core, cavity and part. Check for interferences and cavities, and adjust the tooling as needed.
1. Make sure your part has good integrity, perform a save-as and create a new version of your part. Make this version with added and removed features to create a watertight part. Do not remove any features that are not necessary to remove.
2. Use the new watertight version of the part to Boolean to create a watertight core and cavity. It is recommended to save the core and cavity as separate files.
3. Save the watertight Boolean version of the file as a new file and subtract out the original part. What remains are all the changes you made to your watertight version of the file and nothing else. These will exist as individual bodies floating in space.
4. Of the bodies floating in space, identify which belong on the core tooling, and if any, which belong on the cavity tooling. Boolean unite each of these bodies to the appropriate tool
5. Create an assembly of the core, cavity and part. Check for interferences and cavities, and adjust the tooling as needed.
The Full Process
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